Well completion fluids



t -ne- United States Patent WELL MPLET Gerald G. Priest, Bryan E. Morgan, Melba L. Lytle, and

Joseph A; Caldwell,Houston, and Bertie]. Birdwell, Austin, Tex., assignors,by. mesne assignments, to Jersey ;Production Research Company, Tulsa, Okla., aco:rpo-

Y ration nfplelaware.

Applicafi n Decemberlzl, 19.5 6, sewa- 26. l

V imam, (c1, 2 2189 3- l No Drawing.

rected toa well conipl etionfluid having ajlow fluidloss',

a controllable density heatfstability, and theproperty.

of being non-corrosive to f erro us metals to'which it is' exposedjin weil completion operations. In its; more specific aspects the invention is directed. to awell completion fluid whic h'will not damage or, contaminate formations or zones in the-earth with which it comes into contact.

Current practice when completing well, such as oil and gas wells, through perforatedcasings isfto have drilling fluids, such asmud, salt water, water, or oil, in the well casing and to perforate the casing with. bullet, shaped h rge, hefmiqalf Q uns fi perfor qrs- Whe the pressure of a formation traversed by. the well exceeds he ydrostatic, pressutsfi i a afi l r r the completion depth, it is customary to use weighted salt waterforlnorinalf drilling mud havinga density great enough to exceedformatidn pressure in orderto'control the well whileperfo'rating the casing and performing other routine completion operations, In the case of-a well filled with dfillin'g rriudlwhejnthe casingis perforated, the'drilling mud-flows into the perforations because of the pressure differentialexistinghetween the interior of the'casingand the formation. The perforations are thereby partially or c p y plussedlw th m d' th s pl gg ng i a vated by the heat and instantaneous pressure evolvedby the p opellantpewd rin the sa e or r and the, high explosive in the case of the jetor shaped charge perfora'to'rs'l' Where'chmical or punch-type perforators are, employed, it is not uncommon for the drillingmud to lose water rapidlyto the formation resulting in the drilling mud becomingdehydrated and formingplugs. Data are available which indicate that, such plugs Whether formed by dehydration of the drilling mud by heat, and/or pressure oriby lassjefwareir o h f na on a e diffi lt to remove by subsequent flow" from the formation into the well bore and'tha't'th'e productivity 'ofa perforated interval ina producing formation is significantly reduced Field completion attempts of wells indicate that such plugging of the perforations may cause formationsto be tested as being-non-productive and thereby condemned when actually the formation may contain economically producible oil'of gas. Thus,'itis clear that the problem of plugging ofperforati'ons is serous and is a source of expense in well completions and of erroneous conclusions in exploratory workwhich may cause major hydrocarbon reserves to remain undiscovered.

'Anoth'er'pr'oblern which exists in perforating wells is that'it'is necessary to provide control of the well during perforations." This is accordingly accomplished by maintaining a hydrostatic column 'whieh exerts a pressure greater: than the formation pressure exposed when the casing is perforated, However, to provide a column having a sufficienthyd'rostatic pressure, it is necessary to add" weighting agents" such as bar'ites, sand, and other solid'heavy materials to the fluid column maintained in h n 2,898,294 Eatented 4, 1959 ice As it hasbecome necessary to drill deeper and deeper Wells in search for petroleum-producing formations, the temperatures encountered inthesee deeper wells have increased toan extent that difliculties have been encoun tered. Temperatures of the order of 200 to 250 F; may be encountered oil and gas Wells. At these temv peratures, certain emulsions which may be used as com: pletion fluids may become unstable and resolve into theircomponentparts. Also, where the emulsions contain certain halogenatedhydrocarbons, suchas corbon tetrachlo ride, at the high temperatures to which the fluids are exposed, the particular halogenated hydrocarbons may breakdown to form corrosive fluids which will damage ferrous metal tubing and pipe with which it may come into contact. It is, therefore, desirable to provide a heat stable emulsion which willmaintain'and preserveits characteristics at high temperatures encountered indeep wells and will also benon-corrosive to the ferrous'metal conduits to which it comes in contact. The emulsions of the present invention are suitable adjustedfor heat-stability atelevated temperatures depending on, the temperatures encountered; For example, an emulsion may be provided which is stable at 200 F., while another is provided which is heat stable at temperatures up to 250 F.

' High temperaturesmay be encountered in wells ranging from 10,000 feet to about 25,000feet in wells with a depth where usual operations, are, performed at from about 14,000-feet to about 18,000feet. High well temperaturessmaywalso be encounteredat lesser depths, for example, from about 6,000 feet to about 14,000 feet, depending on the area where the operations. are, being conducted. i

In accordance with the present invention, these several problems in well, and particularly inwell completion and servicing operations, aresolvedbyQproviding an improved well completion fluid'which has'a controllable density, which isIhe'a'tlstable at the temperatures encountered in the Wells, and which is non-corrosive to the ferrous metal conduitsfl. l1

The well completion fluid of the present invention may be describdfbrieflyi as consistingof an aqueous phase and an oily 'phase, with one ofthe phases containing a soluble weightinglagent Theoilypha'seI contains no less than about 10 percent by volume of tetrachloroethyh ene; a corrosioninhibitor is dissolved inone .of the phases in a corrosion inhibiting amount, and the two phasesare formed into 'a stable emulsion byemploying a sufficient amount of an emulsifying agent.

The emulsion employed in the practice of the present invention is: used in the sense ofthe emulsions described in. Sutheimns Introduction .toZEmulsions, Chemical Publishing Company, Inc., Brooklyn, New York, 1927,-

page 1, wherelanemulsioniis describedlas follows: 7

Emulsions are'intimate mixtures of two immiscible ably, the hydrocarbon may have a'viscosity at 60- F. of lessthan about 40 centipois'es.

The'emulsionmay either be heavier or lighter than the drilling fluid and suitably may have a densityin pounds per gallonin therange from about 7 to about 18 pounds per gallon. The emulsion where lighter than the drilling fluid may have a suitable viscosity sufircient to displace the drilling mud and to prevent displacement thereof by the drilling mud. For example, the viscosity of the emulsion replacing the drilling mud may range from about 10 to about 4000 centipoises at 60 F.

TABLE I Water soluble morgamc compounds suitable as wezghtmg agents Name Formula Specific Gravlty Aluminum br m AlBn 3.01 Aluminum chloride A1011 2. 44 Aluminum iodide A113 3. 98 Ammonium bromide NH Br 2. 33 Ammonium iodide Nl m 2. 51 Ammonium nitrate NH4NO3 1. 72 Ammonium phosphate, dibas1c (NH4)2HPO4 1. 62 Antimony triohloride SbCl: 3. 14 Antimony trifiuoride SbF= 4. 38 Barium acetate Ba(CzH3O2)z 2. 47 Barium br e 4. 78 Barium iodide dihydrate 5.15 Barium iodide hexahydrate. 5.0 Barium nitrite 3. 23 Cadmium acetate 2. 34 Cadmium bromate monohydrate Cd(BrO3) 1.1320 3. 8 Cadmium bromide CdBrz 5. 2 Cadmium chlorate Cd(C1O3) 2. 3 Cadmium chloride CdCh 4. 05 Cadmium iodide CAT 5, 7 Cadmium nitrate tetrahydrate. Cd(N 09241110 2. 45 Cadmium sulfate heptahydrate CdSO4.7HzO 2. 48 Calcium bromate monohydrate. Oa(BrOa)2.2HzO 3. 33 Calcium bromide aBrv 3. 35 Calcium chloride CaC 2.15 Calcium iodide Cali 3. 96 Calcium nitrate Ca(Na)a 2. 36 Cuprie bromate hexahydrate C1l(BIOa)2.6HzO 2. 58 Cupric bromide uBra 2. 8 Cupric chloride CuClv 3.05 Cupric nitrate hexahydratc Cu(N0a)z.6HzO 2. 07 Ferric hlor Fefih 2. 81 Ferric nitrate hexahydrate Fe(N 093151120 1. 68 Ferric sulfate nonahydrate Fez(SO4)a.9H2O 2.1 Ferrous bromide FeBra 4. 64 Ferrous chloride FeClo 2. 70 Lead acetate trihydrate Pb(C2H3O2)2.3H2O 2. 55 Lead chlorate monohydrate Pb(ClOa)z.H2O 4.04 Lead nitrate Pb(NO3)- 4. 53 Lithium bromide i r 3. 46 Lithium iodide Lil 4 Magnesium br m de MgBr 3. 72 Magnesium iodide M Tq 4. 25 Manganese bromide MnBr-z 4. 39 Manganese chloride tetrahydrate. MnOlzAHrO 2.01 Manganese io MTIT" 5. 01 Nickel bromide NiBlz- 4. 64 Nickel nitrate hexahydrate Ni(NO3)z.6H2O 2. Potassium acetate KOzHaO 1. 8 Potassium carbonate K100 2. 29 Potassium fluoride KF 2. 48 Potassium iodide TIT 3, 13 Potassium nitrite KNOQ 1. 92 Porn inm nhnsnhate KgPOA 2, 56 Sodium hisulfate NaHSOi 2. 74 Sodium bromide NaBr 3. 20 Sodium chlorate NaClO: 2. 49 Sodium chloride NaCl 2.16 Sodium hydro 'ide NaOFl 2.13 Sodium iodide NaI 3. 67 Sodium nitrate NaNO*: 2. 26 Sodium nitrite NaNOa 2. 17 Sodium phosphate m0nobasic NaH2PO .2H2O 1. 91 Zinc bromide ZnBri 2. 56 Zinc chloride ZnOlv 2. 91 Zinc iodide 7nT-1 4. 66 Zinc nitrate hexahydrate Z11(NO3)2.6H2O 2.06 Zine sulfate... ZnSO 3. 74

There are many oil-soluble organic weighting agents which are soluble in the oily phase of the emulsion employed in the practice of the present invention. The oilsoluble organic weighting agents suitably have a specific gravity in the range from about 1.2 to about 4. These organic weighting agents are illustrated in the following table TABLE II Organzc weighting agents Name Formula Specific Gravity m-Aminobenzoic acid NHZCGILCOOH 1.511 n-Amy1br0mide CH3(CH2)3CH2BI- 1. 218 iso-Amylbromide 1. 22 tert-Amylbromide. 1. 216 Amylbromide H930 CHzBI. 1. 26 Amyliodide(n) CH3(CH2)3CH2I. 1. 51 1S0-A111y1i0d1d6 (oHahoHoHgoHz 1. 515 sec(n)-Amyliodide. CaH'ICHICH3 1. 507 tertAmy1iod1de (GH3)2OIO2H5 1. 471 Amyliodide..- C2H5CH(CHa)CH2 1.524 Anthracene- (C 1. 25 Anthraquinone 1. 438 Asparagin.-. 1. 54 Aspartic acid 1. 66 Benzalbr0mide.. 1. 51 Benzene hexa chlorl e 1. 89 Benzoic acid- 1. 266 Benzanilide. 1. 31 Benzamide. 1. 34 Benzylbromide 1. 44 Benzyliodide 1. 73 Bromal 2. 665 p-Bromoacetamhdea. 1. 77 Bromoacetophenone ormooomnr 1. 65 uBromoaniliue- BrCsH NFl' 1. 80 Bromobenzene. BrCil h 1. 495 Bromoiodobenzeue BiCsHlI 2. 257 Bromoiodoethane (1,1)- 2. 45 1,2Bromoiodoethane 2. 52 Bromoiodomethane. 2. 96 Bromonaphthalene C1oH7Br 1. 605 Bromosuccinic acid HOOCCHrCEBrCOOH 2.07 Bromotolnene BrCtHrC fi 1. 422 Bromotoluene (m) BrC HrCPh 1. 41 Bromotoluene (p). BrCrlLOFf 1. 39 Brnm nform CHBH 2. 89 Butyliodide C2H5CH2CH2I 1. 617 Chlorobromobenzene 1. 63 Chlorodibromoethane. 2. 3 Chlorodiiodomethane CICHI: 3.17 Chlorodiiodo e GlORHII'J 1. Chloroiodoethane. OlCHzCH' 2. 1 Ch1orotetrabrom0ethane- BmCHClBrz 3. 4 Chlorotribromoethane 2. 6 Chlorotribromomethane- B 2. 7 Pentabromoethane BrzCHCBTa 3.4 Tetrabromoethane (syrn). BHCHCHBI: 2. 96 Iod oform C'H'T-r 4 Ethylene Dibromide BlCzHzBI 2.17 Carbon Tetrachloride. C014 1. 595 Dichlorobromomethane 2. 01 Diehlorodibromoethane. C1zCHCHBI2. 2. 39 Dichlorotribromoethane. BrzCC1CHB1Cl. 2. 62 Difluorobromoethane F CHCHrBl 1. 82 Difluorodibromoethane BrzCHCHFa 2.31 Perfluoro-n-heptane 0 F 1. 73 Perfiuorotrimethylpentane 05F 1. 80 Periluoro(o-dimethylcyclo- OBFIB 1. 86

hexane). 1 Trifiuoroethanol perfluoro- (I1C4F9)20 1. 71

dibutylether. Perfluorodiamylether (l1C5F11)20 1. 78 Perfluorodihexylether (nCuF1a)20. 1. 81 Perfluorodimethylhexylamine. CaF1 N(CFa)2--- 1. 82 Perfiuorodipropylethylamine (nC F7)2NCzF5 1.79 Perfluorotripropylamine; (n 3F7)3N 1. 82 Pegfluorotetraethylethylene (C2F5) 2NCF2CF2N(C2F5 1. 86

lamme.

Perfluorotributylamine" (nC4F9)aN 1. 86 Perfluorotrihexylamine (ll-CeFnQsN. 1. 93 Trichloroethylene ClCHCCl 1. 47 Tetrachloroethaue CzHzClr 1. 60

In forming the emulsions of the present invention, an emulsifying agent is suitably employed. The emulsifying agent selected from a large group of emulsifying agents is suitably one which will provide an emulsion of the desired heat stability. Where emulsions having heat stabilities up to 200 F. are desired, the emulsifying agent may suitably be sodium lignin sulfonate in combination with a tall oil ester of polyoxyethylene sorbitol, whereas when emulsions of greater heat stability are required other emulsifiers may be used. Selected Polyfons may be used to confer heat stability to emulsions exposed to temperatures of 250 F. and higher. The emulsifying agent may be an alkali metal salt, an alkaline earth metal salt, or an ammonium salt of lignin sulfonic acids. Purified lignin sulfonic acids may be used in forming thealkali metal salts of lignin sulfonic acids. Such salts are known to the trade as the Polyfons and may have from about 3 percent to about 33 percent of alkali metal sulfonate groups. Other emulsifying agents may include the ammonium salts of lignin sulfonic acids, such as those known to the trade which::specific compounds ;,are. .so 'um lignosulfonate, polyoxyethylene .sorbitan monostearate I polyogryyethylene sorbitan monolaurate; p'olyoxyethylene etheror fa ty alcohol, a tallow alcohol'=ethylene.oxide, product alkylphenoxypolyoxyethylene ethanol; polyoxyethylene lauryl alcohol, polypropylene-polyoxyethylene condensation product, the talloil ester of. :p'olyoxyethylene sorbitoL, polyoxyethylene aklyl phenol, the. mixed resin and fatty acid esters of polyoxyethylene sorbitol, polyoxye'thylerieamine, 'polyokyethylehe ste a r'yl "amine; a polyoxyethylene. .soy been amine, sorbit anses'ciuioleate, calcium li'gnosulfonate, the"sodiinn'lignosulfonates' containing from. ahout 3 3 per- .cent to. .abqut 32.9 percent of 'sulfonategroups, known as the Rolyf o'ns the Or zansggwhichfare ligno- 'sulfonates' an jpolymerizled ammonium li'gnos'ulfonates. Other v dojnipoiinds which may both as film'- I tmfl n agents lese u t e a es P eparing. the W611. fcompletion fluids of; the. present invention mayinclude bntylene-maleic acid copolymer, polyfiq n 'er the any 5 ,f hi A; .r 1 i v:. a: .1 ee' l f iie a n l th typ 'si Ji te q r empl yed. n the pr ent 'ilir tibnfin ia iq ii iii h fi gefrqm b u to 'iibdut 29.. m .P? .-19 i of the external phase of the emulsion The percent by weight ofthe inorganic weighting agent'orfsalt dissc'ilyed in theaqueo us or water phase may suitably range from about ,1 percent up to about saturation. The Weight perjc'e nt..of the organic compound oryveightingfa gent dis solved in the oily phase may range from about 1 percent up to about saturation. W p g Where solids are used of the nt c illustrated before, the'solids; may be employed in .amoun'ts'from abdutv 0.5 gramto about 3.0 grams per 100 of theaqueousphas'e. fl'hesefsolids areparticularly desirablejand useful at elevated temperatures encountered in deep was. a In order toillustrate theinventionfurther, alhumber of compositions were made up wherein low fluid loss completion fluids were prepared, I Thegfollowifiig table sets out the several compositionsjin accordance With the present invention having the desired characteristics.

TABLE in p sifiofisfdrid'pro'pertie s of emulsions con filming calchlQfidehs the soluble weightirig agent idornpositionof lfimulsion Pr pert ies of Emulsion 1 t A r I FhIidELOSS 1 Aque- Composition ofFAque 3:? t External hous- .ous Phase.-Eilm- 1 Oil Phase Emulsifier r 1 ,Phasepf Phase; Strengthening Agent At Room Tem- "'At Elevated j Emulsion Volr Denperature Temperature 2 L Percent H sity,

. if v lbJgal;

OaGh; w g./100 Before After g./100 WM- Vol: Identity mLEx- Aging, Aging, F.. m1./30 min,

ml. Percent Percent ternal nil-.130 ml.[30 j Phase min.

w Y r 1 37.5' Siiltkem.- 0.5' .24. "I: 7515?:- (8)5398 -.Unstab1e.

.5 25.0 ex-29s Unstable.

A 50.0 oxfzggwn 2:0 3.4 rUnstable 5 38:8 }PolyfonH 2.0 10.5 v 9.0 46.8. .2250 :10. ;g; g .}--.;do..;.-. 20 "10.9 "10.0 30.4. '50: 140 "g;3-}.--.do...- 2.0: 10.9 13.8 02.0. 1 an f .40, 50.0 do 2.0 12.7 12.8 53:0.

I If Sample aged in a'olosedkylindeniat 190 -'iacrylates;.osulfonated;polystyrene, a

formaldehydenondmsgrtiqnproduct polymer 15:1,

. ngaddition. to:- .these,components the emulsion the wlellacompletionwfluid of thepresen invention may also feasted pecan- .emp ss i ispe ib s l ds wh sk. ma e11$t estabilizethe.emul ons-1:em n g h l r e um er. e 1

-.persib1e;.-so s ichz ybecm p ma a m n ione ea p it play qd um bemea e c y hm-b mo- ;;n1 te,:1-fine1y divided sili a washed d ign ed kaolin clay, q n eu ea t molc i z V -ash purified Pj- QgWOQd lignin, sulfonated ethylcellulose, nei ly nylta w ls 1 "T .n. 9n-9 e prese'ntl in o0 24h0i1rs on longer, then cooled toroorn temperature and tested.

5; result doubledto convert it to regularAPIbasi s.

It willbe seenfrom an examination of the data in Table 1 1-1 that the composition contained diesel oil angl tetra .chlordethylene in, some instances and. at least one int-stance theoily phase consisted of 'the tetrachloroethylen'e.

The data presentedin the foregoing tableshow that emulsions of low fil't rati on 'rnay be produced. and that "emulsions may' be prepared which are heatstable atelevated temperatures; depending on thecomposition of the emulsion, heat stability at a given temperature may be provide d. M

In the table OX-298 is the trade name for tall oil ester of pblyoxyethylene sorbitol, while Saltkem isthe; trade name"forsodiumlignosulfonate. Polyfon H is a sodium Ii'gnosulfonate "containing; about 5.8 percent sulfonate 5 groupswhich is preparedfrom purified lignin sulfonic e sodium chromate is a preferred corrosion...in-

'- droxide, Polyrad 111'0-A, and F-12'6. Polyrad 11 10-jA is a product of reaction between ethylene oxide anda Weight primary amine. F-1216 is principercent by pally the ammonium salt of perfluorocaprylic acid. Oilsoluble corrosion inhibitors may also be employed in the practice of the present invention, and examples thereof include Rosin Amine D and Texine. Rosin Amine D is a high molecular weight primary amine, and Texine is a proprietary organic compound commonly used in the prevention of corrosion during the pickling of steel and during oil well acidizing operations.

The corrosion inhibitors may be employed in a small but suificient amount, suflicient to inhibit the corrosivity to ferrous metal tubing and surfaces. An amount of corrosion inhibitor dissolved in one of the phases of the emulsion may range from about 0.001 to about percent by weight of said phase.

The Orzans are a new series of surface active chemicals derived from the by-products of wood pulping by the sulfite process using an ammonia base. In this process, wood chips consisting of about 90 percent western hemlock and percent white fir are placed into a digester containing ammonium bisulfite and excess sulfur dioxide. The mixture is then cooked for about 8 hours at a temperature of about 290-300 F., while a pressure of 70-80 p.s.i. is maintained within the digester. After the cooking period, the mixture is filtered to separate the wood pulp from the bisulfite liquor.

Orzan A is obtained by concentrating the liquor by evaporation to about 50 percent solids, and-then-spraydrying the concentrated liquor. Orzan A, therefore, is an unaltered by-product of the pulping process containing ammonium lignin sulfonate and wood sugars.

Orzan S is asodium salt of lignin sulfonate and is obtained by adjusting the concentrated ammonium bisulfite liquor to pH 7.07.5 with sodium hydroxide. At a pH of 7.0-7.5 the excess ammonia is driven oif and the concentrated liquor is spray dried to obtain a free flowing powder.

in Orzan A, increasing their average molecular weight.

The member having the highest molecular weight is Orzan AH3.

The Polyfons are a new series of surface active chemicals based on lignin obtained as a by-product of pulping wood chips using the kraft process. In the kraft or sulfate process, the lignin is rendered soluble by digesting wood chips at about l60-l80 C. with a mixture of one part of sodium sulfide and two parts of sodium hydroxide as a 5 percent solution. From the kraft black liquor the lignin, together with some hernicellulose, is precipitated by acidification with mineral acid. The lignin obtained in this rnanner is purified and then sulfonated to provide the various lignosulfonates such as Polyfon H, XQ, 0, T, R, and F.

A more complete description of processes used in the isolation of lignin and the various lignin sulfonates, i.e., the kraft, soda, and sulfite processes, is given in a book entitled Cellulose and Cellulose Derivatives by E. Ott, H. Spurlin, and M. Grafllin, Interscience Publishers, Inc., New York, ed. 2, part 2, pages 524-545.

The well completion fluids of the present invention are quite useful in wells as completion fluids and as perforat- For example, the compositions are useful as completion fluids to protect perforations from contamination by the drilling fluids and other fluids which may be found in a well bore. For example, if perforation operations are conducted, and it is desirable to rework the well at a vertically spaced apart zone in the well, it may be desirable to protect the existing perforations while the operation is being conducted in the other zone in the well. In that event, the existing perforations would be protected or blanketed by an emulsion of the present invention, while these operations, such as perforating, cementing, treating, fracturing, and the like, were conducted at a vertically spaced apart location.

Likewise, the well completion fluids of the present invention are useful as perforating fluids in that the perforations do not become plugged with debris from the well or with any other material from the formation. In other words, by perforating in an emulsion in accordance with the present invention, not only are the formations prevented from being damaged, but the perforations remain clean of material which might result in a productive hydrocarbon formation being overlooked.

The well completion fluids of the present invention may also be suitably used as fracturing fluids. In other words, where there is a formation of a low permeability and it is desirable to open up a channel therein, the completion fluids of the present invention may be pumped under high pressure into the formation to cause a lifting of the over-burden and thereafter allow an increase in permeability and production of the hydrocarbons contained in the fractured formation.

There are many uses of the well completion fluids of the present invention which will occur to the skilled workman. It is contemplated that the completion fluids of the present invention may be employed to blanket or protect perforations or formations which are exposed in a well while operations are conducted at another location in the well. Likewise, it is contemplated that the existing perforations or exposed faces of formations may be protected while an operation is conducted where the exposed face exists or where the perforations exist.

In order to illustrate the present invention further, a well in Harris County, Texas, was treated to block communication behind the casing between two sands by squeeze-cementing the channel behind the casing. An existing producing interval was to be covered with a nonplugging emulsion of the present invention during the workover operation to protect the perforations.

In this particular operation, the well was killed by circulating formation salt water into the well through production tubing set at about 6594 feet. Two and one-half barrels of an emulsion weighing 10 /2 pounds per gallon and containing Polyfon H as emulsifying agent was employed. This emulsion had a fluid loss of 9 ml. in 30 minutes at atmospheric temperature. The stated amount of the emulsion was circulated to the bottom of the tubing with salt water, and the casing return line was closed. The emulsion was displaced down the tubing displacing the salt water until the body of emulsion covered the perforations. Pumping pressure was about 1100 pounds per square inch when the pumping operation ceased. Pressure in the tubing decreased from 1100 pounds per square inch to 700 pounds per square inch in ten minutes, but held at this point until the casing return line was opened to allow bleedoff of pressure.

The well was then circulated above the body of emulsion with 10 pounds per gallon of mud and the production tubing was pulled. The casing was then perforated at about 6400 to about 6402 feet employing a casing jet gun. Cementing equipment was set opposite the perforations at 6400 to 6402 feet, and sacks of a slow-set cement were squeezed into the perforations. After the cement had set, the cement plug was drilled out and the production equipment run. The well was then swabbed in, and the production rate from the perforations from 6620 to 6622 feet returned to the original value without any difficulty. Since production from the protected interval was regained without difliculty, it was clearly demonstrated that the improved emulsion forms a protective blanket for existing perforations wherein workover operations were conducted at a point vertically displaced in the well.

In another operation in Southwest Texas, it was desired to cement existing perforations in a well casing and to recomplete the well in an upper zone. Thus, cement was squeezed into existing perforations from about 9080 to 9100 feet. With 10.4 pounds per gallon mud in the well, 15 barrels of fresh water were located from about 7400 to 8120 feet, and 12 barrels'of 10.9 pounds per gallon empulsion which contained diesel oil in the oily swabbing,the tubing was filled with oil and'an attempt i made to fracture the formation; The formation did not break down under 5000 pounds per. square inch pressure. ,Ariother z'one'was 'perforated' at 81801038192 feet and 8105 t'8215 feetusihg the same numberbf v.,. 3 1.. i int i rods-to'prtiduce the wel lj.-= -After -a six day pumping est, the well produced 28 barrels of fluid per day with 5 percent salt water.' 11; The nature and objects of the present invention having be gco m'pletely described and' illu str'ated,-' what-=we wish to claimas new and useful and secure by Letters-Patent is: .l. well completion; fluid stable at-welltemperature s cons1sting i of- 1 an aqueous phase and. an oilfy phase,{the aqueous of said phases containing a water soluble weightshots per foot with mud opposite "the perforations em- 5 ploying a"'casing"jet gun." 'Iheftubingwithifdual type completion equipment and astretightflow choke'was r'e's et between the two intervalslan the lower acne in the'well wasflowed t'o' the'wastelp the tubin'g'.'t=;:

Tubing pressure "was" 1025 pounds per squareinch while the well was flowing. Production from the casing side through the protected perforations from 7131 to 7144 feet and from 7149 to 7156 feet flowed at the rate of 1491 M c.f. gas per day. The calculated open flow potential was 16,500 M c.f. gas per day from the protected interval.

An emulsion comprising saturated calcium chloride solution, Saltkem, OX-298, diesel oil, and tetrachloroethylene was used as a perforating fluid in a Southwest Texas well. The purpose of the workover job was to exclude the production of water from the existing perfo tions and'to recomplete the well in an upper zone if Li The plugback squeeze job was performed against the 7 existing perforations at 6910 to 6922 feet and 10 feet of cement was left on top of a packer set at 6885 feet. With mud in the well, 20 bbl. of the 11.5 pound per gallon emulsion were spotted in the 5 /2-inch casing from about 6170 to about 6600 feet. The interval from 6483 to 6496 was perforated with four shots per foot using a casingjet gun, and the tubing equipped with a drill-stem-test tool was set above the perforated interval in preparation for testing. The drill-stem-test tool was opened for 8 hours and 40 minutes and then closed for 2 hours and 40 minutes. During a 4-hour interval of this test, the well produced at the rate of 83 barrels of oil per day through a As-inch choke with a maximum surface pressure of 1525 p.s.i. After the test had been completed, the tubing equipped with a packer was set at 6339 feet, and the well was allowed to flow. The well produced 87 barrels of 43.0 API gravity oil from the 6483 to 6496 foot interval through an -inch choke. The tubing pressure while the well was flowing was 600 p.s.i., and the gas-oil ratio was 1676 cubic feet per barrel.

In addition, a considerable number of other field perforating jobs have been made with emulsions having a similar composition as that used in the immediately preceding'example; in these operations emulsions having densities ranging from 10 to 12 pounds per gallon were used in amounts in the range from 5 to 20 barrels.

In addition, an emulsion comprising saturated calcium chloride solution, Saltkem, OX-298, and tetrachloroethyelne was used as a blanketing fluid in a well in the Gulf Coast of Texas.

The purpose of the workover job was to treat the well with a production stimulant and to protect the treated formation with a blanket of non-plugging emulsion until the well could be produced.

. The pump, rods and tubing were pulled out of the 5- inch casing and tubing equipped with a packer was set at 7295 feet. Eighty-eight barrels of 1 percent well stimulant dissolved in lease oil was pumped into the formation through the perforations from 7361 feet to 7368 feet. Five barrels of non-plugging emulsion were pumped .into the tubing behind the stimulant oil solution to protect the newly treated formation from salt water. The tubing and packer was pulled and reset with a pump and byvolume ofltetrachlqrothylehe', a corrosion. inhibitor dissolved in =one of-said -phases in a eqrrosion inhibiting amount, f; an emulsifying agent---suitablean amount fsufli cient -to formj said-phases into alzieait- -stable emulsion; at well temperatures ranging up 10250 2. A wellcompletion fluid inaccordance with clam 1 in which the oily phase comprises ahydroearbon having 'a viscosity at 60 F;-less than about- 40centipoises and in which the oily phase comprises from about 5% to about by volume of said emulsion.

3. A well completion fluid in accordance with claim 1 in which the corrosion inhibitor is sodium chromate dissolved in the aqueous phase of the emulsion.

Y 4. A well completion fluid in accordance with claim 1 in which the aqueous phase contains a water-soluble inorganic metal salt as a weighting agent.

5. A well completion fluid in accordance with claim 1 in which the oily phase contains an oil-soluble organic compound as a weighting agent.

6. A well completion fluid in accordance with claim 1 in which the oily phase comprises diesel oil.

7. A well completion fluid in accordance with claim 1 in which the oily phase comprises kerosene.

8. A well completion fluid in accordance with claim 1 in which the oily phase comprises gasoline.

9. A well completion fluid in accordance with claim 1 in which the oily phase comprises gas oil.

'10. A well completion fluid in accordance with claim 1 in which the emulsifying agent is a salt of lignin sulfonic acid.

11. A well completion fluid stable at temperatures im the range up to 200 F. in accordance with claim 1 in which the emulsifying agent is a mixture of sodium lignirr sulfonate and a tall oil ester of polyoxyethylene sorbitol- 12. A well completion fluid stable at well temperatures: consisting of an aqueous phase and an oily phase, the: aqueous of said phases containing a water soluble weight-- ing agent, the aqueous phase consisting essentially of from about 5% to about 95% by volume of the emulsion-i and the oily phase consisting essentially of from about; 5% to about 95% by volume of the emulsion, said oily' phase containing fromabout 10% to about by volume of tetrachloroethylene, and one of said phases: containing from about 0.001 to about 5% by weight of a corrosion inhibitor, and an emulsifying agent in am amount in the range from about 0.5 to about 20 grams: per 100 ml. of the external phase of the emulsion suitable to form a heat stable emulsion at well temperatures: ranging up to 250 F. p

13. A 'well completion fluid in accordance with claim: 12 in which the oily phase comprises diesel oil.

14. A well completion fluid in accordance with claim: 12 in which the corrosion inhibitor is sodium chromate;-

15. A well completion fluid stable at well tempera-- tures in the range up to 200 F. consisting of an aqueous phase and an oily phase, the aqueous phase consisting;

,of a saturated solution of calcium chloride in an amount 0.001% to about 5.0% by weight of sodium chromate as a corrosion inhibitor, and an emulsifying agent in.-

11 I an amount in the range from about 0.5 to about 20 grams per 100 ml. of the external phase of the emulsion consisting of a mixture of sodium lignosulfonate and tall oil ester of polyoxyethylene sorbitol.

V 16. A well completion fluid stable at Well temperatures in the range up to 250 F. consisting of an aqueous phase and an oily phase, the aqueous phase consisting of a saturated solution of calcium chloride in an amount from about 5% to about 95 by volume of the emulsion and the oily phase consisting of from about 5% to about 95% by volume of the emulsion and containing l V 12 12 in which the emulsifying agent is an ammonium salt of lignin sulfonic acids.

18. A well completion fluid in accordance with claim 12 in which the emulsion consists of equal volumes of the aqueous phase and the oily phase and in which the oilyphase consists of a mixture of diesel oil and tetrachloroethylene and the emulsifying agent is an alkali metal salt of purified lignin sulfonic acids.

References Cited in the file of this patent UNITED STATES PATENTS 1,829,705 Walker Oct. 27, 1931 2,073,413 Cross et al. Nov. 25, 1936 2,297,660 Mazee Sept. 29, 1942 2,476,845 'Dawson July 19, 1949 2,661,334 Lummus Dec. 1, 1953 2,748,084 DeLew et al. May 29, 1956 2,764,242 Rohrback et al. Sept. 25, 1956 2,805,722 Morgan et al. Sept. 10, 1957 

1. A WELL COMPLETION FLUID STABLE AT WELL TEMPERATURES CONSISTING OF AN AQUOEOUS PHASE AND AN OILY PHASE, THE AQUEOUS OF SAID PHASES CONTAINING A WATER SOLUBLE WEIGHTING AGENT, SAID OILY PHASE CONTAINING NO LESS THAN 10% BY VOLUME OF TETRACHLOROTHYLENE, A CORROSION INHIBITOR DISSOLVED IN ONE OF SAID PHASES IN A CORROSION INHIBITING AMOUNT, AND AN EMULSIFYING AGENT SUITABLE AND IN AN AMOUNT SUFFICIENT TO FORM SAID PHASES INTO A HEAT STABLE EMULSION AT WELL TEMPERATURES RANGING UP TO 250*F. 